The films of Mike Leigh have always come dangerously close to finding genuine human idiosyncrasies on cinematic landscapes. Few times have these portraits been happy ones, from the existential nausea of Naked to the “kitchen sink” social realism of Vera Drake and All or Nothing. Leigh’s explorations have differed depending on context, but the characters in his films all seem to confront the same dilemma, one of horrifying banality, of life rendered mundane by an impossibly large, indifferent universe.

With that in mind, it’s incredibly jarring for us to encounter a character like Poppy (Sally Hawkins), whose named itself implies a kind of buoyancy she exhibits with every word, every mannerism. Poppy mumbles and beams and giggles at each turn, voicing every possible thought that pulses through her head with a twinkly smile. She never stops smiling, or bouncing, or tittering, no matter the occasion. Her wrists and ears are adorned with jangly hoops; every piece of clothing she wears is a primary color. Poppy is, as the title suggests, Happy-Go-Lucky, a woman who radiates happiness like a ten-thousand-watt bulb. In a way (and God forgive me the comparison), she reminded me of the slightly insane, paste-fetishistic Miss Lippy from Billy Madison - both are loopy, spirited primary school teachers! But Poppy emerges as more than a caricature, however eccentric. She’s the kind of person hardened cynics like “the rest of us” want to shake by the shoulders, to wake her up to the childlike dishonesty that is optimism, to show her the real world.

And that’s exactly what the world (or at least Mike Leigh’s world) does to Poppy. Life seems to greet her proselytizing affirmation with, at best, incredulity, and, at worse, repulsion. As Poppy flits about through pleasant episodes of normalcy, she’ll encounter a number of new people in various stages of life’s arc - a troubled young student in her class; a maddened old derelict; her manic, insecure sister, and Scott (Eddie Marsan), a comically high-strung, fuming driving instructor, all of whom threaten her with a disillusionment that seems long in coming. But by film’s end, something much different is happening. Poppy’s dissonant positivity has smoothed into something we accept; she’s no longer obnoxious, foisting her manic cheerfulness on everyone around her, but triumphantly fighting for a better life. And this won’t be a fight without casualties, of sorts.

Poppy’s clashes with Scott become the real conflict of the film. Scott is a lost soul, enraged and almost unhinged by the world around him, a world which foils his attempts at control and order. His rages take the air of comical tantrums until we realize they come from a genuinely darkened heart. Scott is both lured to and maniacally frustrated by Poppy, who casts off his grasp for order with a shrug of her shoulders. He loves and hates her obliviousness because his own disappointments have eaten him from the inside. Poppy finds in Scott, perhaps for the first time, a person who is not only impervious to her brand of kindness, but repelled by it. This is man she won’t be able to stop from destroying himself.

Leigh paces Happy-Go-Lucky with leisurely, unhurried episodes. He and his actors’ famous use of improv help hew close to moments of real human serendipity, of life caught unawares. This is a director who has mastered his game over the course of decades, and he doesn’t hurry the film’s emotions or tones. Leigh hints that Poppy is struggling against Modernity’s oldest crisis, a Dostoyevskyian alienation born of urban rot, but this is essentially a character study and a critique of modern happiness, and a powerful one at that. Maybe Poppy’s outlook is a foolish one, blinded as it is to trenchant realities, but by film’s end her vision is no longer a dishonest one. Poppy remains an improbably good, happy person, not in spite of the unhappy world around her, but because of it. She listens to a vagrant’s ramblings; she listens to her abused, innocent student; she listens to Scott’s wrathful sorrow; she listens to her whingy, neurotic sister. All of these people, whether directly or indirectly, insist that she “take life seriously,” and yet are the unhappiest of all. And Poppy listens, trying to understand just what they’re missing, and what she has. How do you tell a person that, simply, life is sweet?

Phillip Stephens is the lead critic and book editor for Pajiba. He lives in Fayetteville, Arkansas.